Serota noted that the payments are required by law, and said he believes the administration has the legal authority to continue making them despite the court cases. He warned of “turmoil” as insurers finalize their rates for 2019.

America’s Health Insurance Plans, the main health insurance industry trade group, said in a statement that it is “very discouraged” by the Trump administration’s decision to freeze payments.

“Costs for taxpayers will rise as the federal government spends more on premium subsidies,” the group said.

Rumours that the Trump administration would freeze payments were circulating late last week. But the Saturday announcement via email was unusual for such a major step.

The administration argued in its announcement that its hands were tied by conflicting court rulings in New Mexico and Massachusetts.

Medicare and Medicaid Administrator Seema Verma said the Trump administration was disappointed by a New Mexico court ruling that questioned the workings of the risk program for insurers.

The administration “has asked the court to reconsider its ruling, and hopes for a prompt resolution that allows (the government) to prevent more adverse impacts on Americans who receive their insurance in the individual and small group markets,” she said.

More than 10 million people currently buy individual health insurance plans through HealthCare.gov and state insurance marketplaces. The vast majority of those customers receive taxpayer subsidies under the Obama-era health law and would be shielded from premium increases next year.

The brunt of higher prices would fall on solid middle-class consumers who are not eligible for the income-based subsidies. Many of those are self-employed people and small business owners, generally seen as a Republican constituency.

The latest “Obamacare” flare-up does not affect most people with employer coverage.